Regular expression for decimal number accepting 0 to 4 digits but no characters

Question

I'm trying to devise a regular expression which will accept decimal number up to 4 digits. I have successfully done it when a user types it in a text box. Now, I'm trying to validate text box for paste operation. For that, I have written a jquery function

 function pasteNumber() {
        var reNumber = /\d*\.\d{0,4}/;
        var theString = window.clipboardData.getData('Text');

        if (reNumber.test(theString) == false) {
            alert("You are trying to paste an invalid Number!")
            return;
        }
        event.srcElement.value = theString
        return;
    }

The regular expression which I have used is accepting a value like

44.aaaa

which it should not accept. Then I tried changing regular expression to

/\d*\.\d{1,4}/

Then, it started to accept values like

44.1aaa

I need help to write a regular expression which will accept values like

4.1
421.11
467.111
438904.1111
0.1

But not

1234.a
489.a
435.aaa
412.1aaaa
1567.11a

In short, there should be no characters.

Any suggestions please? Thank you

Answer 1

You are only missing the anchors ^ and $

^\d*\.\d{0,4}$

See demo

But, to avoid matching . and 123. , you can enhance it as

^\d*\.\d{1,4}$

See update .

As for anchors , they

do not match any character at all. Instead, they match a position before, after, or between characters. They can be used to the regex match at a certain position. 在特定位置。 The caret ^ matches the position before the first character in the string. Applying ^a to abc matches a . ^b does not match abc at all, because the b cannot be matched right after the start of the string, matched by ^ .

Similarly, $ matches right after the last character in the string. c$ matches c in abc , while a$ does not match at all.

Answer 2

You just need to add some anchors and group (?:) the entire decimal part and make it optional with a ? :

^\d+(?:\.\d{1,4})?$

^ is for start of string, $ is for end of string

See demo